1. Field of the Invention
This invention relates to a method for activating zeolitic compositions of matter suitable for use as catalysts for isomerizing or cracking hydrocarbons. More particularly, it relates to a sequential procedure for activating crystalline zeolitic aluminosilicates which contain at least one kind of alkaline earth cations as a substantial portion of its cationic requirements.
2. The Prior Art
Crystalline zeolitic aluminosilicates, often referred to as molecular sieves, of themselves or as components of a catalyst composite are now well known for their usefulness as catalyst for the conversion of hydrocarbons. Various methods have been disclosed for use in activating and/or improving the activities of these materials. There is, of course, no procedure which is generally suitable for the activation of all such catalysts. Whether or not an activation procedure is required and what the procedure should be is a matter which is intimately associated with each specific catalyst and one for which the requirements usually vary widely.
In U.S. Pat. No. 3,390,101 a method is disclosed for activating crystalline aluminosilicates in which at least 10% of the total sites available for cations must be occupied by hydrogen. The activation procedure comprises in sequence a reduction and an oxidation step in which the temperature for the reduction step is in the range 600.degree. to 1400.degree. F (315.degree.-760.degree. C), preferably 800.degree.-1200.degree. F (426.degree.-648.degree. C), and seldom exceeds 1400.degree. F (760.degree. C). The procedure of the present invention differs from the foregoing procedure in that a crystalline zeolitic aluminosilicate having an alkaline earth as a substantial portion of its cations, and being substantially free of hydrogen cations is modified or activated by at least one particular sequence of treating steps, including the use of a temperature in the reduction step which is in the range above 700.degree. C and below a deactivating temperature (920.degree. C).